1. Field of the Present Disclosure
The present disclosure relates to a reverberant sound adding apparatus for adding a signal representing a reverberant sound to an input audio signal.
2. Description of the Related Art
Techniques are known that simulate acoustic characteristics of a prescribed space and add signals (reverberant sound signals) representing reverberant sounds of the space to an input audio signal (input signal). In these techniques, output signals that are obtained by adding reverberant sound signals to an input signal are supplied to speakers and sounds with the reverberant sounds are emitted from the speakers.
One physical factor that influences the auditory impression of the reverberant sound is a temporal density (hereinafter referred to as a “sound density”) of a sound that constitute the reverberant sound. The auditory impression corresponding to the sound density of the reverberant sound will be referred to as a “density sense” of the reverberant sound. For example, the reverberant sound having a high sound density causes a densely packed impression, and the reverberant sound having a low sound density produces a sparse impression.
The sound density of the reverberant sounds depends on the kind and the details of an input signal, the acoustic characteristics of a space, and other factors. Therefore, the sound density of preferred reverberant sound also depends. For example, whereas reverberant sounds having a relatively high sound density are preferred as reverberant sounds to be added to a sound of a musical instrument, such as drums, that produces short, strong-attack sounds, reverberant sounds having a relatively low sound density are preferred as reverberant sounds to be added to a sound that is generated when classic music is played in a concert hall with long-lasting reverberations. As a result, there is a demand that the sound density of the reverberant sound be controlled to a proper value according to the kind and the details of an input signal, the acoustic characteristics of a space, and other factors.
JP-A-2000-069598 (for example, paragraph 0008) discloses, as one technique for controlling the sound density of reverberant sounds, a technique that increases the density of generation of an audio signal using an allpass filter. Whereas a reverberant sound adding circuit disclosed in JP-A-2000-069598 that includes a comb filter and an allpass filter can generate a reverberant sound while increasing their sound density, it cannot reproduce acoustic characteristics of a prescribed space because it is not of a convolution type using an impulse response (a physical quantity representing a temporal response that represents acoustic characteristics of a prescribed space; hereinafter may be referred to as IR).